Bleeding brakes?

[SMOKEU]

I'm currently in the process of bleeding the front brakes on a GSXR600. How do I know when all the old fluid is out? How much fluid (approximately) should the front brake system hold all together?

Also, there are plenty of tiny air bubbles (about 0.25mm wide) in the hose I'm using to bleed the brakes. Is this a big problem? I'm always fully tightening the bleed nipple before letting the brake lever go.

[Fast Eddie]

you might be lucky and find the fluid capacity of ur brake system and could measure the amount thats come out and once uv hit the capacity measurement u know it must be out.. but u prob wont.

if the fluid is older/darker color then wait til u see fresh fluid coming out.. should be a slight color dif unless the fluid u have in there is very new as well.

[Fast Eddie]

keep going until the air bubbles stop..

once fully bled there should be a solid stream of fluid out of ur exit tube. make sure ur exit tube goes into a container which already has some fluid in it, submerge the end in the fluid to stop it sucking air up that way. and make sure its nice and tight over the bleed nipple..

keep going til no air comes out is the key ;) enjoy. it can take quite a while.. also dependant on ur technique eh. there is a trick to bleeding

[mossy1200]

Take the bleeder hose in a loop so that you dont suck any air back at any point.tap the caliper every so often also to move any air up towards the nipple exit.You should see a colour difference when the new fluid is coming out the bleeder hose.normally you will need suck the filler bottle down several times and maybe use 50ml each side on a twin disc front for a good job.

[Madness]

Another tip is to tie your lever back to the bar and leave the system open to gravity bleed slowly overnight.

[SMOKEU]

There are no air bubbles coming out of the calipers, only coming through the other end. Also there's no difference in the fluid colour. I'm not sure when the brakes were last flushed as I've only had the bike for 3.5 months.

[mossy1200]

There are no air bubbles coming out of the calipers, only coming through the other end. Also there's no difference in the fluid colour. I'm not sure when the brakes were last flushed as I've only had the bike for 3.5 months.

Shouldnt be bubbles at the top end.

[Fast Eddie]

Shouldnt be bubbles at the top end.

yea what he said..

your saying there are bubbles coming up in the ur fluid reservoir?

I dunno, isnt that a sign of dodgy seals in the master cyl or caliper? I'v never had bubbles coming up that end

[FJRider]

Easiest way to clear the lines of old fluid is to remove ALL lines from the bike. And blow air through them ... And start from empty.

[mossy1200]

It sounds to me that you need a master cylinder kit or theres crap under the plunger thats pressurising the line.When you squeeze brake with lid off reservoir and holding rag to stop squirt of fluid hitting bike(cover your tank and paint work and dont look dirrectly down into reservoir from above) a jet of fluid should squirt up when you release brake lever. slowly ok

[Subike]

self bleeding brakes is very easy to do.
you need the right tools
One 500 mill empty bottle.
One 300mmm length of flexible plastic pipe.
One bottle of new fluid.
One ring spanner the size of your bleed nipple.

Place 50mill of fluid in the empty bottle,
Remove the cap of the master cylinder.
Remove dust cap from bleed nipple.
Loosen bleed nipple to finger tight.
place felxi tube over bleed nipple, ensure its a tight fit.
place the other end of the flexi tube in the bottle,
ensure the open end of the tube is immersed in the fluid.
(this will ensure that no air return sup the tube when releasing hand lever.
loosen bleed nipple.
Operate brake lever with smooth even strokes.
keeping a watch on the level in the master cylinder, topping it up with fresh fluid as it is pumped out.
Your old fluid will be pumped visa the tube into the jar.
No air can return up the tube as long as it is immersed in the fluid in the bottle.
You will be able to see the clean fluid entering the tube once you have pumped out the old fluid.
Tighten the bleed nipple, replace dust cap over nipple.
Replace master cylinder cap once the proper level has been put in it.
repeat with the rear brake.
Discard the fluid in the jar when finished, DO NOT REUSE

Thus you have bled your brakes and replace all the old fluid with new fluid.
You should do this at the end of winter every year before you start your summer riding.

This is a one man operation, and not difficult to do.

[mossy1200]

Questions..

was the bike spongy brakes or was it not releasing the pads from discs after braking before you started?

[unstuck]

Because I read the op it sounds to me like he has air in the tube he is using to bleed the system with.May just be that the tube is not a tight enough fit around the nipple.:yes:

[SMOKEU]

Shouldnt be bubbles at the top end.


yea what he said..

your saying there are bubbles coming up in the ur fluid reservoir?

I dunno, isnt that a sign of dodgy seals in the master cyl or caliper? I'v never had bubbles coming up that end

Sorry I should have been more clear. There were no air bubbles coming from the master cylinder or from either caliper. The bubbles were coming up from the bottle where I drained the fluid into, but no bubbles managed to get into either caliper.


Questions..

was the bike spongy brakes or was it not releasing the pads from discs after braking before you started?

Brakes were great even before I replaced the fluid, I just wanted to change it because I'm taking the bike to Ruapuna this Thursday and want the bike to be in the best possible condition for the track.

[mossy1200]

Sorry I should have been more clear. There were no air bubbles coming from the master cylinder or from either caliper. The bubbles were coming up from the bottle where I drained the fluid into, but no bubbles managed to get into either caliper.



Brakes were great even before I replaced the fluid, I just wanted to change it because I'm taking the bike to Ruapuna this Thursday and want the bike to be in the best possible condition for the track.

The tube running into your catch bottle is clear and you can see the fluid moving through it.Just making sure sorry.
It seems all your doing is getting rid of air in the system like you should be.keep going till fresh fluid comes out and small bubbles stop.
Better still we want video footage.

[Fast Eddie]

Sorry I should have been more clear. There were no air bubbles coming from the master cylinder or from either caliper. The bubbles were coming up from the bottle where I drained the fluid into, but no bubbles managed to get into either caliper.

sweet, sounds normal, yea if air bubbles are coming up from the catch bottle they are coming from the fluid ur draining out of the system eh. keep going to bubbles stop.

she'll be right

[p.dath]

sweet, sounds normal, yea if air bubbles are coming up from the catch bottle they are coming from the fluid ur draining out of the system eh. keep going to bubbles stop.

she'll be right

Brake fluid should be clear. As water attacks the fluid it turns more and more brown.

Keep flushing it until clear fluid is coming out - like you are adding in.

Also don't let the fluid get on anything as it is very corrosive. Wash it off anything it gets on anything.

And don't forget to flush the back brake while your at it ...

Also break fluid doesn't tend to keep that long in a bottle (maybe 6 months), and you have to keep it tightly sealed. If it is not clear when you go to use the bottle again throw it away.


Also when completely finished check the reservoir and make sure it is not overfill (which you can do by accident if you are also changing the pads). If the reservoir is overfill, and something expands in the braking system you may suddenly discover your front brakes locking on while you are riding ...

[SMOKEU]

Thanks for all your advice everyone! Job is done now so after that oil change I did today as well as the brake fluid the bike is track ready for Thursday.

[helenoftroy]

Thanks for all your advice everyone! Job is done now so after that oil change I did today as well as the brake fluid the bike is track ready for Thursday.

Be warned young one ! the track is seriously addictive & fantastic fun.... have a great day on Thursday

[SMOKEU]

Be warned young one ! the track is seriously addictive & fantastic fun.... have a great day on Thursday

I've been once on the old CBR250 I used to have. Best day out ever!

The whole day is only costing me $50 since ACC are paying the rest, and once I've had my Ohlins suspension setup properly, my GSXR should be a real track weapon*.










*with a good rider (eg, not me!)